The boiler efficiency is given by (where m = Total mass of water evaporated into steam in kg/h, mf = Mass of fuel in kg/h, C = Calorific valve of fuel in kJ/kg of fuel, h = Total heat of steam in kJ/kg, and hf1 = Sensible heat of feed water in kJ /kg)

• A. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/288-116-1.png">
• B. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/288-116-2.png">
• C. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/288-116-3.png">
• D. <img src="/_files/images/mechanical-engineering/steam-boilers-and-engines/288-116-4.png">